Automatic telephone system



Nov., 9, i943.. N. H. sAuNDERs I AUTOMATIC TELEPHONE SYSTEM Filed Feb. 2, 1942 14 Sheets-Sheet l S R E D N U A S H N AUTOMATIC TELEPHONE SYSTEM 14 sheets-sheet 2 Filed Feb. 2. 1942 OmN ,IlaxllL v NNN kbbkvmwu .7271/527 Ur'.- Nrm ENHUHEPE,

Nw., @g w43.. N. H. sAUNDERs i AUTOMATIC TELEPHONE SYSTEM Filed Feb. 2, 1942 14 Sheets-Sheet 5 www Nw., @s w43., N. H. sAUNDERs AUTOMATIC TELEPHONE SYSTEM Filed Feb.' 2, 1942 14 Sheets-Sheet 4 14 Sheets-Sheet 5 Nov. 9, 1943.. N. H. sAUNDERs AUTOMATIC TELEPHONE SYSTEM Filed Feb. 2. 1942 5a. NE@ m29 muv ".IIHL

H1@ r. mw .m .E

Ev mmv N@ 5m x mi?. mma

Nov. 9, 1943. N. H. sAUNDERs AUTOMATIC TELEPI'IONE` SYSTEM 14 sheets-sheet e Filed Feb. 2. 1942 0V. 9, 1943 N. H. sAuNDERs AUTOMATIC TELEPHONE SYSTEM Filed Feb. 2, 1942 14 Sheets-Sheet 8 [7L/E27 Uff Nov. 9, 1943v l N. H. sAuNDERs 2,333,744

AUTOMATIC TELEPHONE SYSTEM Filed Feb. 2, 1942 14 sheets-sheet e 622 sus/v vE/v 000 To F/G. 3 CA-l/M CA- TM 5-777 14 sheets-sheet 1o Filed Feb. 2. 1942 lbmwmhvmw\ @wpwb.,

HUE/Z7 02".' Mrmaniazmder if 5? y.,

N. H. SAUNDERS AUTOMATIC TELEPHONE SYSTEM Nov. 9, 1943.

Filed Feb. 2, 1942 14 Sheets-Sheet 11 kbby a S 4 S S S S WOO` v ...Hl www JNMIXU Nov. 9, 1943.

N. H. SAUNDERS AUTOMATIC TELEPHONE SYSTEM Filed Feb. -2, 1942 14 Sheets-Sheet l2 Nov. 9', 1943. N. H. sAUNDERs AUTOMATIC TELEPHONE SYSTEM Filed Feb. 2. 1942 14 Sheets-Sheet 13 y 72H/En 721' Nrmanhfnds'm Ilm,

Rn, Rv@ Run ,Gun Ruh, h. @M ma. Tm.

s m n n my# ma v* mm wi. w.

Nov. 9, 1943. N. H. SAUNDERS 333,744

AUTOMATIC TELEPHONE SYSTEM Filed Feb. 2, 1942 14 Sheets-Sheet 14 I I I I I I I I FOU/P 5E C ONU/M Y GROUPS I I I I I I I I I. I1 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I L I /00 mf @fol/P119 jl/'rmnff 55212757515 Patented Nov. 9, 1943 AUTOMATIC TELEPHONE SYSTEM Norman H. Saunders, Chicago, Ill., assgnor to Kellogg Switchboard and Supply Company, Chicago, El., a -corporation'of Illinois Application February 2, 1942, .Serial No. 429,232 40 claims. (ol. Ivo-1v) i invention relates.to automatic telephone systems, and its Vobiectis tri-provide an economical vand `reliable automatictel'ephone system arrang led to provide the kvarious `services which have heretofore been found necessary or desirable in connectioniwith the subscriber linesf` `This application is a continuation in part of my prior application Serial No. 466,990, led July 3, 1ML 1 f,

. ,GENERAL DESCRIPTION In addition toproviding regular telephone service lfor individual subscriber lines, it is necessary or at lea-st desirable that automatic telephone sys? tems provide the following services:

` 1. Party-line service, which includes the selection of .the called party line andthe signaling of the desired substation thereom..7^

Reverting-call party-line service, inlwhich a` ,subscriber at one substation on `a party line is able t0 call a subscriber at any other substation on the saine party line;

3. P. B. X. service, the provision of a group of subscriberI lines having a common directory num'- ber,4 with arrangements for selecting and making connection with an idleline. of the group when the common. directory number is called;

4.` Non-busy-line service, the provision of alinev which is not made busywhen called, enabling a number of contemporaneous calls to be made to such line: l t

5. Call-holding service, the provision of arrangements for enabling calls to a desired substation to be held therefrom, as when a` subscriber is being annoyed by anonymous calls;

6. Secretarial service, the provision enabling the callsk directedto a substationl While thesubscriber isl absent to be routed to a seoretarys telephone; and y y '2. Intercepting. service,.the provision of arrangements enabling calls to a" disconnected substation tobe routed to. an intercepting operator.

It is an object ofthe invention to provide services such as those mentioned above through the provision of equipment common to all of thecon-4 capacity switches heretoforeV used as line nders and connectors. The disclosed tandem arrangee ment of the small-capacity snrzitchesV incorporates a number 4orfeatures of improvement to those previously enumerated. f

Aslwill bedescribed more fully hereinafter, the subscriber lines aredivided into/what are termed large groups (of 100 lineseach) ;Y subgroups of small-capacityprimary and secondary switching devices are provided in each large group to handle both the originating and terminating calls; and control equipment common to all the primary and secondary switching `devices of a large group is provided t0 position these devices `for extending originating or under-action connections, whicht vcommon controlequipment also responds in addition to position the requiredprimary and secondaryy switching devices to complete terminating of con-` nector-action connections, the dialed lineLdesignating digits for each `call being stored for this purpose and then transferred, call-by-call, to the common equipmentas the common equipment becomes available.

`A specic object is the pr duction of a system of thecharacter under thelconsideration wherein control equipment common to all ofthe primary and secondary 'switching .devices of a large group is provided to control the setting of these devices vinoutgoing of finder-action connections,which common equipment also responds in substantially the same way to position the required vprimary arid'secondary switchesv for incoming or connector action, the dialed tens and units digits for eachV call beingstoredior this purpose and then transferred, call-by-call, to the common equip'- l ment as itv becomesavailable. l

hector-action connections) is greatlyreduced;

A feature of the disclosed `arrangement is `that the-digitstorage equipment isassociated `With the connecting-link circuit- (the circuits which control the setting-up of incoming or con- A further feature is that thel distributing device associated withweach such link circuitV has access to'eachjsecondary -device allottedto extend connector-action calls to the primary/devices, whereby no connectoracf tion calls need be lost at any time'because of lunavailability to the connecting-link circuits of idle connector-action secondary devices. Y Y

A further specic object is the production 'of a system of the charaotel` under consideration wherein the equipmentfor providing Aservices such as those enumerated hereinbefore is providedin connection with the above-mentioned common equipment, whereby the amount of equipment necessary for providing such services Other lobjects and features of the invention will The drawings Fig. 14 shows the intended arrangement ofk the sheets of drawings of which Figs. 1to 11 are drawn. n

The system arrangement Referring now particularly to Figs. 12 and 13, the arrangement of the system will be described. The arrangement shown in Fig. 12 illustrates a 1,000-line automatic telephone system comprisf ing ten 1D0-line groups, each of which may be arranged as indicated in Fig. 13. Each of the rectangles in Fig. 12 indicates' a separate 10D-line group, each such group having' originating-link paths taken for use automatically by primary and ,secondary finder action within the group when the receiver is removed ata calling substation,

each group also having terminating or connectoraction link paths, any idle one, of which may be seized when a connection is to be completed to a subscriber line of that group.

The selectors SI, SII, etc. to 59|, located respectively'below'the 10Q-line groups, #1, #2, etc. to #are each but one of a number (ten, for ex'- -amplel provided to handle calls originating in the kassociated D-line group. In the 'illustrated 1,000-linesystem, only a single rank of selectors is employed, the 'illustrated hundreds'selectors. If the system illustrated werev expanded to a y10,000-line system, two ranks.; of Aselectors would be provided, thousands selectors'and hundreds selectors; while if-it were reduced'to a 10D-line system, no selectors at-all would berequired, each loriginating or finder-action path being joined to a `terminating or connector-action path, as will be understood.

' l'Ihevillustrated selectors, mechanically, may be of the usual two-motion type of automatic switch. Where long-life is a factonthe selectors may be of the so-called allrelay type, in which a counting-relay operation occ-urs responsive to dialed impulses to select any one of ten group relays, folflowed by'a hunting-relay'action to select an idle link connected up by the group relay operation.

One selector of the latter type suitable for use Y.herein is illustrated in applicants co-pending application, Serial No. 346,069, filed July 18, 1940, issued April 14, 1942, Patent No. 2,279,531. Considering, for example, the selector SI of Fig.

.12, therectangle within which the reference .character SI is placed may indicate the control .relays of the selectors, while eachl of the short,

heavy linesbeneath this rectangle is intended to ,indicate a4 group of Contact sets (assumed to be ten in the present example).V Each-of these groups of contact sets is connected `up responsive .to the dialing of a separate one of the digitsl 1 to ,9 and 0, as indicated. The fainter lines extending horizontally between illustrated selectors are intended to indicate the multiple between selectors.

-k 'I he links .incoming to thev 10U-line group #l V are reached from the rst, or digit-1, groupof contact sets of all of the'selectors; the links incoming to the 100-line group #Zare reached from the second, or :digit-2, grouper contact sets of all of the selectors; etc., to the 1D0-line group #0, whose incoming links are reached from the tenth, or digit-0, group of contact sets of all of the selectors. l

Since the arrangement of any one of the 100- line groups may be similar to those of all of the rest of the 1D0-line groups, it suffices to show the switching and circuit arrangements of` a single one of the 10G-line groups. #9 has been chosen arbitrarily for this purpose. It is the 10U-line group who-se incoming links are reached through any one of the selectors respon,

sive to the dialing of the digit 9. The switching arrangement of 10G-line group #9 is shown in Fig. 13, while the circuit arrangements thereof are indicated in Figs. 1 to l1. 1

Referring now particularly to Fig. 13, it will be seen that the selector S8! of Fig. 12 is only one of tenselectors provided for vhandling calls origi i nating in 10D-line group #9, the other selectors being S82 to S90, the respective groups of contact sets of all of these selectors beingv connected "in multiple with each other and 'with the corresponding groups of contact sets'of the selectors reached from the other 10Q-line groups.y n

The one hundred subscriber lines served by 100- line group #9 are subdivided into ten Vlil-line groups, each served byA a separate group of primary switching devices. For example, the tlrst lil-line groupin Fig. 13 comprises the subscriber lines 9II to 9I0, indicated along the top of the drawing and connected in multiple to the selective-position contacts of the four primary switching devices IPA, IPB, IPC, and IPD. These switching .devices constitute the rst or ten primary groups. The second primary group, including primary switches ZPA to 2PD, serves the second 10-1ine group (lines 92| to 9,20) of the100.- line group #9. The primarygroups serving/the third t'o eighth 10-linev groups have y,been omitted' for.v the sake` of compactness, but the primary switching devices (SPA to SPD land IOPAto` NPD) which serve the ninth and tentnlO-.line groups are indicated.

The lines and line multiple for all of the lll-line groups except the rst, have been romitted forjthe sake of simplicity, as each 10-line1group yis similar to each of 'theother 10-lineV groups.,` "It is intended to be illustrated bythearrangement'in Fig, 13 that any idle oneof therprimary 'sw itcl`r'--V ing devices, such as IPA to IPD, for example,

having access to a groupof 10 lines can operatel tomake connection with a calling line, and that any idle one of the said devices can operateto been provided on the assumption that four'connections (incoming, outgoing, or both) 'within a 10-line group are sufficient.` For the 10U-line group, this provides for a total-oi forty connections to be made with 'calling and' called lines, which has been shown by experience to be much more than is required. Accordingly', thetotal number of connection paths is halvedin the secondary groups, as will now be pointed out.

As niustratea in Fig. 13, a' total of twenty" secondary switching devices (each of 10-line ca- ISC to 5SC` inthe C group, and ISD to -5SD inl the D group. In each secondary group, the selective-position contacts of the switching devices are connected respectively in multiple as indi- 'Ihe 10G-line group l aesarea 3 cated, and the ten links thus provided extend respectively to ten primary 'switching devices, each in a different lO-line group. The five secondary devices 'ISSA to 5SA, comprising the A secondary group, have access to the 'ten A primary devices 5 lIPA to IDPA; the B secondary group has access to the ten B primary devices ll-"B vtoV NJPB'; the C secondary .group has access to the ten C primary switching devices IPC to IOPC; and the D secondary group has access to the ten D primary vswitching devices IPD to lilPD. Each of the twenty secondaries, ISA to 5SD,'therefor-e, has access toV each ofthe lil-line groups-'cf lines, through the illustrated primary switching devices. 'I'he common secondary devices are thus 15 restricted to a small or lil-line group, as is the 270 case of the primaries. The reduction permitted in the number of switching devices vor links when the group is enlarged is well known, and therefore need not be further discussed herein.

some in each group are allctted to the handling of the originating or nder-acticn connections, the remainder being allotted to the handling of terminating or connector-action connections. It

is to be observed that devices ISA to SSA in secondary group A, Iare assigned to finder action, and are linked respectively to the selectors SSI to S83 the .devices ISB to SSB in secondary group B .are linked respectively to the selectors SM to S85; and the first two devices` in each of the 3,5

C and D secondary groups are linked respective-ly with the selectors S31 to Sil-tl. The tenrernain-yJ ing secondary switching devices (the last-*two in each of secondary groups A and B, and the last three in each of the` secondary lgroups C and VD), are assigned to connector action, and are therefore linked to the selective-position. contacts of the distributing devices, such as DR-l and DR-2.

Since the 1D0-line groupshown infFig. 13y is 45 group #9, calls to this group come through the ninth. group of contact setsl of all of the selectors serving all 1D0-line groups. Il-he link group reached through the ninth yselector 'group of contact sets is shown by a single line extending to the left from selector SBI, and then branching out upwardly into ten lines to indicate the ten link paths represented by the ninth vselector group.

These link paths are all incoming to the 10G-line group #9 of Fig. 13, and they eXtendrespective-ly 55 to connecting-link circuits CLC-.I to CLC-I9, of which only the first two are indicated.

Each connecting-link circuit CLC-4y to GLC- `IIJ has a selective-switching .device associated The dis'- 60 therewith termed herein a distributor. tributors DR-I and DR-2 are shown associated respectively with the connecting-link circuits CLC- l and CLC-2. Each of the distributors has ten selective-position Contact sets, whereby it can associate its individual connecting-link circuitwi-th any one of the ten terminating or connector-action paths leading to the secondary devices assigned to connector action.

The circuit drawings 7.01

most portion of Fig. 3 is common `equipment con- 15 v transfer Vrelay |01, for changing over from finder action'tc connector action; test-cutoi relay |02, matching control relaysv i113 to |96, controlled according tothe instant position of the preference group .of relays |01 to ||'0 to matchen idle one of the four primary switching devices in a calling (or called, .as the case may be) IO-line `group with a secondary group in which there is at least'one idle secondary ldevice allottedfor finder action (or for connector action,` as `the case may be).

Fig. 2 Vshows ten pairs of tens-connecting relays, each pairbeng associated with a separate one of the ten lil-line groups. `Relays 20| and 22| |4 are associatedwith the first Iii-line group; 2|l2'and `2f|2 are associated with the second 10- lne'group, etc., to the last pain-'relays 2m and 220, `which are associated with the tenth ill-line group tion and for connector action and are arranged to be mutually exclusive in their operation. Each Of the twenty secondary switching devices, 275

or the relays 20| to 2| D has ten contact pairs,

but for the sake 4'of compactness of the illustration,'only the rst, second, ninth and tenth contact pairs are illustrated. The relays 22| and 222 are control relays associated with the group relays 42|| to 22B. i

' The relays 23| to 24|) are associated respe`ctively with the ten lO-line groups, and each of them serves as a cutoi relay to disconnectthe associated l-line group from finder action, when `a call is made from a linel therein at a time when at least one of Ytheprimary switches of the group is idle, but a busy condition in one or more of the secondary groups `precludes theA completion of the lnder action. The-timer RT associated ,withy the relays 23|- to 249 is arranged to unlock any Qperated one of these relays at frequent ntervals (every ten seconds, for example) to permit a further test to be made. Relays 223 and 224 are ycommon relays associated with cutoff relays 23| to 24|) to bring about the operation thereof as above pointed out.

VThe uni-ts translator shown on the lower part or Fig. 3, comprising the relays 39| to 386-, is operated over conductors to (l of theycable CA-'UM through contacts of any one of the relays 2|J| te 2H! to energize the conductors I to (i in the cable CA-PM according to the required setting of the relays in any one of the four .switching devices of any primary group, such as the switching devices IPA to` |PD, Figs. 4 and that two lines of the same l0-line group arev calling simultaneously.

Although the system arrangement herein disclosed is not limited to any particular form of small-capacity switching device, it has been chosen` to illustrate the invention as applied` to 4a system 'using al1- relay lsmall-capacity switching devices at'the primary, secondary, vandfdis". tributor stages. ,1,

The switching devices IPA and IPD of Fig. 13 are each shown in full vin Fig. 4, but switching devices IPC and IPD of Fig. 13 are eachindicated in Fig. 3 as a broken-line rectangle,v for each ofl these devices may be similar to the devices IPA and IPB. 'l

The switching .device IPA, for example, in- -cludes the ve 'selecting relays 4II to 4I5, each of. which has two sets of selective-position contacts thereon. row (three contact pairs to a set) `are assigned respectively to the iirst to fifth lines,l of the yassociated 10-lineV group, while the five contact sets shown just below the ones last named are assigned, respectively, Vto the* sixth to tenth lines in the associated 10-line group. The switching device IPA includes also a sixth or switching relay MB, which remains normal when connection is to be made, through the concerned one of the relays 4II to M5, with one of the first five lines in the group, but is operated, along with one of the-relays MI to M5, when connection is to be made with any one of the sixth to tenth lines in the associated 10-line group. The other smallcapacity switching devices are similar. In addition to the relays MI to M5 which cooperate as previously7 pointed outto select any desired one of the illustrated ten Contact sets, the switching device IPA has associated therewith a connection relay MU which, among other things, when operated, connects up the'oonductors I to 5 of the cable CA`PM to permit setting of the relays M I to M6 according kto the marking placed on the conductors of this cable by the units translator of Fig. 3. i The hold relay 4I'I is associated with the switching device to exercise certain control vfunctions to be hereinafter described.

Also shown in Fig. 3 is a'broken-line rectangle indicative of the primary groups 2 to 10.` It is to be observed that the primary marking cable Cfr-PM extends dotted through this brokenline rectangle, which is intended to indicatethatthis cable multiples into the switching device of each of the primary `gr'ou`ps12 to 10 as indicated in connection with the primary switching devices IPA to IPD of Figs. 4 and 3.

Of the teny subscriberlines served by the priv `mary switching devices IPA to' IPD of Figs.r` 4 `and 3, only the first and sixth lines (#QII and #8!6) are shown. The tip, ring, and sleeve conductors T, R,Vand S of each 'of these lines are Ymultipled to the corresponding selective-position contacts of the associated primarydevices IPA vto IPD. The illustrated rst and sixth lines are 'served byrelay MI of device IPA;` the second relay M2 serves the second andv seventh lines; the third relay M3 serves the third and eighth lines; the fourth relay M4 serves ythe fourth and ninth lines; and the fth relay M5 serves the fifth and tenth lines of the associated 10-line group.

Line #SII is the line of substation A, while line #SHG is the line of substation B. Line and cutoff relays 49| and 462 are individual to line f #SIL while line and cuto relays 483' and 404 are individual to line #SNL Whereas, the lines #SII and #BIB Vare individual (or single-party) lines, Fig. 4A shows lines #Sill and #El I8 which are party lines. Line #9H is illustrated as a ten-party line having substations #SI'II to #QI'III thereon, of which vonly substations #SI'IL #9I'I5, and #BI'I rare shown. The line #SIS is shown as a four-party The contact sets in the upper line, having substations #9I8Ito #9I84 thereon. The line equipment ofline #9 I8 comprises line and cut-off relays 46| and 462 as in the case of the individual lines. The line equipment of line #SIL vin addition to line and cutoff relays 45tV and 452, includes lockout relay 453. Y This lockout relay is arranged to enable the exchange switching equipment to be entirely disconnected from the line while a reverting-call conversation is being carried on over the line, which conversations are likely to be quite frequent because of the large number` (10) of substations connected to line #9I'I. As will be pointed out hereinafter, the common control equipment is arranged to distinguish between a party line Vwith a lockout relay and a party line without a lockout relay, and to disconnect the switching equipment from a party line over which a reverting'call has been made, only in the event that such party line is equipped with a lockout relay.

Fig. 5 shows the secondary switching devicesiSA and SSB of Fig. 13, each of which diiers from one of the primary switching devices (such as IPA, Fig. 4) in that there are four contact pairs to a set (tip, ring, sleeve, and hold).

Fig. 6 shows the distributor DRP-I of Fig. 13,r as well as the selector SSI. sumed to be of the so-called al1-relay type shown in applicants Patent No. 2,279,531, issued April 14, 1942, hereinbefore referred to. Of the relays of this selector, only the switching, line, and release relays 62| to 623, one of the hunting relays' 624, and the group #9 relay 625 are shown. The other circuit apparatus and conductors of the selector are omitted, as the details of the selector form no part of this invention.

The connecting-link circuit CLC- I of Fig. 13

is shown in Figs. 7, 8, and 9. This connectinglink circuit is accessible to the selectors over the tip, ring, and sleeve conductors T, R, and S ex,- tending to Fig. '7 from Fig. 6, and it is interconnected through cable CA-DR-I to the distributor DRf-I, Fig. 6.

The connectinglink circuit CLC-I includes the illustrated control relays IIlI to 'III kof Fig. 7;

the control relays 8M to 80'! of Fig. 8; the tens, units, and partyregisters TR, UR, and PR. of Figs. 8 and 9.' and control relay 9| I of Fig. 9.`

Along the lower portion of Figs. 8 and 9, andV in Figs. 10 and 11, there is shown common equipment which is a portion ofy and supplemental to the common equipment of Figs. 1 to 3. The two portions of the common equipment are interconnected vby the tens and units marking cables CA--TM and CA-UM.

The portion of the common equipment shown in Figs. 8 and 9v includes the marking terminal blocks B TM and B-UM; control relays 8H) and Slil; and the tens, units-and party-identifying terminal bioeks B-TL B-UI, and B ,PL 'remporary jumpers may be attached to the abovementioned blocks for marking and identifying purposes. I' The portion of the common equipment shown in Figs. 10 and llincludes control relays I DUI to IMQ, IIBI and HD2, and the common-test equipment CT. The common-test equipment CT includes control relays H03 to' H09. The common test equipment CT is connected by cable CA-CT to all of the connecting-link circuits, such as CLC-I,of the same hundreds group.

DETAILED DESCRIPTION Thedisclosure having been described generally, a detailed description of the operation of 'thedis- This selector is as-` A call from substation-,AA to;4 substation B A description will4 first be given of the operations involved.v when the subscriber at substation A calls the subscriber at substation B. A

It is to be observedthat thenumber of the line of substation A is 911, and'. that the numberxofthe line of substation BY is 916, the lines being: both lines of thesame large (1D0-line.) group, and both of the same small; (1U-line)` group; From2 the description which is to follow;Y it wi1l1= be understood how any line: of the system can callanyotherline thereof.

In order to cause av connectionlto-becompleted from the calling line 911 -to-thle.` called' line 9161, the subscriber at substation A: removes receiver; waits for dial tone,which he hears when connection has been extended to. a selector; and then dials the hundreds, tensg; units digits; 9, l, and G-in the desired number, followed? by the nal digit 1 to cause ringingscurrent to be applied to the called line.

Marking the calling IU-Zirie group and ili calling Zine therein j When the receiver (not. sho-wn) isv removedfat substation A, line relay-4|l1r energizes. cverthe calling line; Assuming that at least one ofthe primary'switching; devices. lPAto IPD (fligsafliand` 3) having access to the lO-line group irnwhich the calling line is located is idle the closureof the inner contacts of line relay dllfl places a starting batteryV poten-tial on conductor ST "ot the #il tens-group cablev Cil- GII over the following circuit path.: from battery,y byfway of the resistor 409, conductor 198,l contacts ofany unoperated one of the holcllre'lays (such as: tI-7|` and. 421)! of the assocated pri-mary group., conductork 419-11,

conductor M36, common to ally relays of the first i lO-line group, inner contacts of the operated line relay lll'I, to conductor 405.

At its lower contacts, linerelayd-'I pl'acesj` a marking ground potential' on conductor I iin-cable CA-G-I. The tens andL uni'tsdesig-na-tion oi the calling line isy thus markedin cable CAe-GII'. I

Assuming that the operation of the line rel-ay llII'lI occurs-at an instant when: allfoff thetensi relays :HI to 220l (and consequentlyA vrelaysA lil'` to tact ofl group=cutoi relay 23|", windingA ofgroup relay 20|, ,the lower Winding of: grouplrelay' 211i, normallyl closed contacts controlled by thelower armature of'relay 2 II, common conductor'zir, the inner lower contacts of allof the group'I relays 22|J'to 2| I in series, and thence to grounditl'rrou'gli contacts of; clearout and transfer-control# relays 222 and 22|. over this circuit.

Operating the. omitsI traf/islctor UT Upon operating, relay 20| connects thamark conductors I to20 of the groupl cable CA-Gtrespectively with lthe conductors ofv `units-,mark cablev CA-UM. The ground potential Aplaced on the individualrnarkng conductor I, in thefgroup-l cable Cil-GI by the lower contactsof li-ne relay |||l|I isv thereby extended,v th-roughthe uppermost Grouprelaysl 2o! and 2"-I-Il operate A marking cable CA-UM closing ay circuit through the outermost' contacts? or? relay;- 3061; upper. wind.i ing of relay 3M, inner upper contacts; of relays 302 to 305; and thenceto battery' throughl the associatecli resistor. Relay` 304i operates over this circuit. Atitsfupper armaturie it placesja: markinggro-und! potential` on conductor. If of:v the: pri-,- mary marking cable CAMPM, tr/hilegatitsv lower armature it connects conductor 4If im cable GAP-UM to the marking relay Sigbut relay 306 is. not operated. at thisY time, sinceftlae conductor Ii in. cable CA-UM is grounded only whenthe sixth line a; tens group.- is calling or' is` being called', lin which case, relaysfilli andf arefboth operatedv to; ground both:V thee first. and the sixth conductorsfin cable CAP-PM. 'Y y At this point itf should be notedthat` thefrelays 3IIII- to 306- are so= connected. that the mariee,

ing of only a sing-le line can. be impressed. upon the conducto-rs oil cable Cia-BM, evenfthough two or more linesin the! samer() linegroup. aref calling simultaneously'. E01' exampla, when.V relay, 3|J|loperateswl 1ich it. does, when any one of the siX-thto tenti-Limes in a.y iodine group is calling or is 'beingy called, it disconnects'tlfie com ductors If to,- 5 .ot the cable CA-UM, associated respectively Withtlie first to! fth lirresofA a group-whereby? only the4 six-th to.` terittr` conclue torsijn' cable CA-UMlafne effective tofoperatethe relays. 30| to SM5z undergthat condition. VThe battery-chain contacts carried lbyrelays,3&2 toV 395 insure that 'notwoof.` these` relays. can. be operated at. the sanieytime. As an additional safeguard, the. grou-nd. potential.. throught which conductors 2 to 5` offthe; cableCA-,EM canrbe marked is: carriedlthrough cha-ine contacts of ree lays 30| to-3|14 y A flfhe ground potential applicator conducton l.

Lot cableI UCA-@Ms is,J eiiective` to1 position whichever; one; ot the primary, switclfling;` `devices LBA to IPD becomes connected unA to extend `the callinglina@ y I l SeZecting'f the primary sim'tchfitgrMr fi/eviccs in 'tite callin-gf 10-Zittegroup Y I Upononeratingfover its. previously traced. cir-` cuit,. relay 2H',` at `its lower,ar1 iiat'ur,e;,`locks the lower terminalof its lower windngtoground throughf contactsotf relays; 222 and 221',V atl/the sameA time disconnecting itsQl'ow'er fwi'ndingl'from the. common conductor 21295.. At'its. inner armaature, rela-y 21|. disconnects ground potential from l'soncuctlgn:` 229'," to. tl'iereby` prevent opera-4 tion of any `further'. group; relays. oyen a' circuit such as, that aboveft'racfed. Thernova," of ground potentialv frein, conductor`` 222| 'also prevents operation off transfer-control ,relay 22h until Ythe Vcurrent finder actionr has beencorn` pleted; l E, `Relay 2.1i also QonneCtSLVthecQnduCtbrsAll to lf3.- of the primary-control cable CPL-PC' respec-` ti lyto. the. conductors A, to D of the first-group primary-control'. cable'.` lCA-PC] thereby Select-A ingthe group git-primary switching devices (tPA to-'|PD) havingaccess. tofthe lid-line, group` con--` tai-nin'g the calling line.A K' Y Materna@ mi faire'` primero device. an idle ftnder-actionsecortdcryfgrot/rrV Ari idle primary switching. device-ni theM @am ing. primary groEuf) is now'to be' Inatcli'edwitlr one, of the` secondary groups having,f an'fikle finder-action secondary "devicef ittici-eiligr respon! sive't'o the'y described eonnectingun of they con` ductors of the cable CA-PCI. sumed that therelays |01 to ||0 of the preference group PG are all in their illustrated restored condition at this time, in which event secondary group A has the preference, for ground potential is extended (through contacts of relays and |08) directly to the inner armature of the Avrelay |03 of the matching-control group MC.

Let it be assumed now that all four of the primary switching devices IPA to IPD, Figs. 4 and 3, of the selected primary group are idle at this time. lIn this event, all fourof the concerned hold. relays, such as 4I? and 421,- are restored, and battery potential is applied through al1 four of the connecting relays, such as 4|0 and 420, to all four of the conductors A to D of the associated primary-control cable CA-PCI. Battery potential is thusextended, through contacts of the operated group relays 2| I, and over the four conductors of cable CA-PC to the junction of the windings of the respective relays |03 to'I06 of the matching control group MC. Let it be assumedV further that there is at least one idle Ender-action secondary in each of the four secondary'groups. In this event, there is ground potential on the upper terminal of the upper winding of each of the relays IOI to |06, as will now be pointed'out. It is to be observed that the finder-action# secondary cable CA-FS leads from equipment illustrated in Fig. 1 to the four secondarygroups,` carrying 12 conductors, including Vgroup conductors GA to GD, associated respectively with the finder-action secondary devices in secondary groups A to D. As shown in Fig. 5, conductor GA in cable, CA-FS, is common to the finderaction secondaries in secondary group A, and is supplied with ground potential through'co-ntacts of the hold relay 501, asflong as the secondary device ISA is idle, and is similarlyv supplied with ground potential at each other idle'inder-action secondary device in group A. Similarly, conductors GB to GD in cable CA-FS extend to the iinder-action secondary rdevices in secondary groups B to D, respectively. By thisarrangemena under the present assumed conditions, each of the conductors ,GAto GD of cable CA-FS is grounded, whereby ground potential, through contacts of the unoperated relays |0| and |02, is applied tothe upper terminal of eachof the relays |03 to |06 of the matching control group MC, and all four ofthese relays operate, each` in series with the connecting relay (such as I0 and 420) of the corresponding primary device IPA to IPD. None of the said connecting relays, however, can operate at this instant because of the indicated c high resistance of the upper windings of relays With preference ground potential applied, as described, only to thearmature of the A relay |03, only relay |03" can lock itself operated, through its lower-resistance lower winding. Each of the relays |03 to |06 closes an operating circuit for test-cutoff relay |02, whereupon relay |02 opencircuits the upper winding of each relay |03 to |06, whereupon relays |04 rto |06 immediately restore. Relay |03, however, remains operated, and relay 4I0 operates, in the following locking circuit: from ground, through contacts of the unoperated relays ||0 and |03, lower armature and front contact of relay |03, the lowresistance lower winding of relay |03, conductor A of cable CA-PC, `contacts of relay 2| I, con-v ductor A of cable CA-PCI, contacts of the un# It may be as-V operated hold relay 4I1, and the winding of necting relay 4|0, to battery.

Finding'the calling Zine l con- The primary switching device mais selected by the operation ofconnecting relay l||0 over its above-traced circuit, in series withthe low-resistance lower winding of the locked matchingcontrol relay |03. Relay 4|0 connects they conductors to .B of the primarymarking cable CA-PM respectively with. the selective relays 4||. to 4|6. Conductor of cable CA-PM'has been marked by ground potential applied thereto as previously described at the units transla' tor UT, Fig. 3, conductors 2 to 6 of this cable being unmarked. As a result, relay 4|| operates, but relays 4|2 to l||6 remain unoperated;

Upon operating, relay 4I| connects up the tip, ring, and sleeve conductors T, R, and S of the #1| and #6 lines in the associated 10-line group, but 'the connecting up o f the #S line is ineiective at this time because switching relay y4|6 `re` mains unoperated, and only the #I line of the group (the calling line #9| I) is eectivelycon, nected up. The tip, ring, and sleeve conductors of the Acalling line #9H are Vthereby extended, through thel uppermost set of contact pairs of relay 4H, and thence through contacts of the unoperated switching relay M6, to the tip,rring, and'sleeve conductors ofthe primary linkPlA, extending to the secondary multiple in theA secondarygroup.

Marking the actuated primary switching device The'actuated-Vprim'ary switching device' IPAyisv marked in. the A secondary multiple to enable the'nder-action secondary switching device-in the A group which isto operate to make connection with the actuated primary device IPA. This marking is accomplishedyonly during the time connecting relay M0 is operated, being accomplished as follows: V

Connecting relay 4|0 applies ground lpotential to the markingconductor M2 (not used on any of the primary switching devices 4accessible through selective positions l to 5 of Va secondary switch), and it applies amarkingground poten/-y tial through contacts of hold relay 4H, to the marking conductor Ml, illustrated as includedA in the primary link P|A,y extending: to the secondary` multiplefof the A-secondary group.

matched A group As a further result of its above-described operation, matching-control relay |03 connects up conductor CA of the cable CA-FS, to prepare for theVV selection of a finder-action device in the Asecondary group. f

At its lower armature, test-cutoff relay |02 closes a circuit, through contacts of'relayf I|0, for the upper winding of relay |09 of the .preferencengroup PG, whereupon relay |09v operates and applies ground potential to conductonlfll',

with reiays ma to los restored, and relayflbz, 

